Method and means for dry enameling



y 1964 J. A. WARD 3,132,038

METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 '7 Sheets-Sheet 1 JOHN A. WARD ,4 T TOP/V 7 y 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING D R Y e r m am .A r S9 MW A m w mm 7 N m w.

Filed Jan. 29, 1960 y 5, 1964 J. A. WARD 3,132,038

METHOD AND MEANS FOR DRY ENAMELING A TTORNEY May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING '7 Sheets-Sheet 4 Filed Jan. 29, 1960 INVENTOR JOHN A. WARD lllll lllllli llllllllll ATI'OAV/VEY 7 Sheets-Sheet 5 INVENTOR.

JOHN A. WARD May 5, 1964 J. A. WARD;

METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING 7 Sheets-Sheet 6 Filed Jail. 29, 1960 JOHN A. WARD May 5, 1964 J. A. WARD METHOD AND MEANS FOR DRY ENAMELING Filed Jan. 29, 1960 7 Sheets-Sheet 7 INVENTOR JOHN A. WAKD rray/vs) United States Patent METHOD AND MEANS FOR DRY ENAIWELING John A. Ward, Leorninster, Mass, assignor, by mesne assignments to American Radiator & Standard Sanitary Corporation, New York, -N.Y., a corporation of Delaware Filed Jan. 29, 1960, Ser. No. 5,405

14 Claims. (Cl. Mi -1%) piece is first heated to a temperature above the fusing point of the enamel in powdered form referred to herein as powder and of thereafter applying the powder to the heated 'work piece so that the powder fuses thereon to form the enamel coating.

' In present practice the workpiece, such as a metal bathtub or sink, is first placed in a furnace where its temperature is raised above the fusing point of the powder. Thereafter, the work piece is removed from the furnace, and workmen manually apply the powder to the heated work piece in such a manner that an even coating of powder is appliedand bonded to the work piece before it cools below the melting point of the powder. This present method has two serious disadvantages, one of which is the necessity for the workmen to apply the powder in a room having'a relatively high temperature and also of their working in close relation to the heated work piece which has a very high initial temperature of the order of 1100 F. to 1600 F. This requires the workmen to wear suitable asbestos aprons, mittens and arm protectors and other protective gear which hinders their movements and which also prevents them from working for more than a few minutes at a time on the dry enameling process. V i

In addition it is often necessary to return the metal work piece to the furnace several times during the dry enameling process to re-heat it above the melting point of the glass powder since the work piece cools rapidly at the powder applying station even though the room may be at a temperature as high as 130 'F.

- The reheating slows down increases its cost. r The applicationof powder to the work pieces by the present 'manual operation is done by specialized workthe enameling process and 'men who become highly skilled in the enameling operation; The production rate for'the enameled articles" thus is entirely dependent upon the supply of such skilled labor and this dependence uponthe labor supply tends to limit increases in output as the training of new workers is a.

long process. a

Accordingly, it is an object of the present invention to provide a method and means of automatically "applying powder to the heated workpiece. This will permit the powder to be applied in an antechamber to the main heating furnace which antechamber may be maintained at a temperature considerably above that which could be-main- ,tained where the powder was manually applied. Thus,

the methodand means of the present invention alsoprovides an antechamber adjacent to and communicating with the main heating furnace to which the heated work piece may be moved when it has been heated to a proper dry enameling temperature and in which it may be kept during the entire dry enameling operation. This antecham:

her, for example, may be maintained at a temperature'of' ice about 800 F., and this significantly reduces the cooling rate of the heated Work piece and thus provides a considerably longer period during'which the dry enameling operation may be carried out.

Another object of the present invention is to provide a dry enameling operation which is almost entirely automatic and which requires a minimum of supervision.

Another object of the present invention is to provide a method and means for dry enameling which is more rapid than the present manual methods. g

Another object of the present invention is to provide an automatic dry enameling method and means suitable for irregularly shaped articles. 7

Another object of the present invention is to provide an automatic method and means which is easily adjustable for use with a wide range of article shapes and sizes.

Other and further objects of the invention Will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forminga part of the specification, wherein:

FIG. 1 is a side elevational view partially in section of the dry enameling means in accordance with the present invention; I

4 FIG. 2 is a horizontal sectional view of thedry enamel- 7 ing means taken along line 22 of FIG. 1;

FIG. 3 is a vertical sectional view of the dry enameling means taken along line 33 of FIG. 2;

. FIG. 4 is a side elevational view of the work piece tilting and rotating jig;

FIG. 5 is a front elevational view of the jig of FIG. 4; FIG. 6 isa top plan view of the jig of FIG. 4;

FIG. 7 is a fragmentary top plan view. of an auxiliary powder feeder;

FIG. 8 is an enlarged sectional viewiof the powder feeder of FIG. 7 taken along line 8-8 of FIG. 7; T

FIG. 9 is a fragmentary top plan view of the main powder feeder;

FIG. 10 is an enlarged sectional viewtaken along line 101il of FIG. 9; p

FIG. 11 is an enlarged fragmentary perspective View of a portion of a powder feeding comb;

FIG. 12 is a diagrammatioperspective view partially in section illustrating the feeding of powder on an irregularly shaped work piece in accordance with the present invention;

FIG. 13 is a diagrammatic perspective view of another powder to an irregucation of powder to the irregularly shaped work piece.

General Description The dry enameling method and means of the present invention will first be described generally with particular reference to FIGS. 1-3. a

As illustrated in FIGS. l-3, the dry enameling apparatus 1 comprises a furnace 2 in which the coated work piece 3 which is to be enameled is initially heated to a temperature above the melting point of the dry powdered vitrifiable enamel. The work piece illustrated in these figures is a lavatory or basin but any article requiring enameling may be similarly handled. The coated work piece 3 is initially positioned in the furnace 2, having a sliding door 4 and is heated therein to a temperature above the melting point of the powder which typically is between 1100 F. and 1600" F.

An enclosure or antechamber 5 is provided adjacent the furnace 2 in which the automatic dry enameling operation is carried out after the furnace 2 has heated the work piece 3 to a suitable dry enameling temperature. When the temperature of the work piece 3 has been raised to the enameling temperature, the work piece 3 is moved from the furnace 2 into the antechamber 5. The antechamber 5 is heated by a suitable means so that its temperature is kept well abovethat of the surrounding room to reduce the cooling rate of the work piece 3 and to cause it to remain above the melting point of the glass powder for an appreciable period during which the automatic dry enameling operation is carried out.

As illustrated in FIGS. 1-3, the work piece 3, when positioned in the heated antechamber 5, is mounted on a movable work piece holder indicated generally at 6. As will be more fully described below, the holder 6 provides for rotation of the work piece 3 about a horizontal axis and an axis perpendicular to the horizontal axis which permits the work piece 3 to be moved in a desired predetermined pattern during the application of the powder. The powder is applied to the 'work piece 3 by a main powder feeder 7 and an auxiliary powder feeder 8. The powder feeders 7 and 8 supply a continuous and controlled sheet of falling powder to predetermined surfaces of the work piece 3 to cause the work piece 3 to be enameled with an enamel coating of predetermined area and thickness. The rate and pattern of fall of the powder from both the main feeder 7 and the auxiliary feeder 8 are controlled as also is the movement of the work piece 3 by the holder 6 to provide for an even coating of enamel over the irregular surfaces of the work piece 3 during the enameling operation as will be described below. As the powder from the feeders 7 and 8 strikes the surfaces of the hot work piece 3, the powder melts and forms a smooth enamel coating of predetermined thickness.

Thereafter, the work piece 3 is removed from the hot antechamber 5 and is permitted to cool causing the enamel to harden.

A rail mounted fork lift 9 is preferably provided to move the work piece 3 into and out of furnace 2 and the antechamber 5.

Work Piece Holder The work piece holder6 is illustrated in detail in FIGS.

4-6 and comprises a jig 11 adapted to mount the particular work piece being enameled. In order to expose all of the surfaces of the work piece which are to be enameled to the powder which is being applied by the feeders 7 and 8, the jig 11 is mounted for a simultaneous rotational and tilting movement.

The tilting movement is provided by having the jig 11 mounted upon an arbor 12 which is mounted for rotation about a horizontal axis by the pivotal mountings 13 and 14 on the stationary frame 15. The angle of tilt of the arbor 12 is controlled by a reversible tilting motor 16 (FIG. 1) through the intermediation of suitable sprockets 17 and 18 and a connecting chain 19. The suitable controls are provided to change both the speed and direction of the tilting drive motor 16 so that the arbor 12 and the work piece on the jig 11 may be tilted to the desired working angle or may be continuously moved through a 4 predetermined path by suitable automatic controls as the powder is applied to the work piece.

In general it is desirable that the surface of the work piece being enameled be positioned as nearly perpendicularly as possible to the direction of powder fall to facilitate the even distribution of the fluxed powder on the hot metal surface. The arbor 12 is positioned by the tilting motor 16 to accomplish this result for the particular work piece being enameled. Since the work pieces generally have irregular shapes, the entire surface being enameled cannot be horizontally positioned; however, a compromise position is determined which places the surfaces which are being enameled as nearly horizontal as possible. I

In order to provide for an even distribution of the powder, it is desirable to provide for the movement of the work piece 3 beneath the falling powder. This is done by having the jig 11 rotatably mounted on the arbor 12 on a suitable shaft 20. The shaft 20 is driven by a jig rotating motor 21 through the intermediation of a suitable connecting means. Inthe preferred embodiment illustrated in FIGS. 1 and 4-6, the drive connection comprises a drive gear 22 attached to the bottom of the rotatable shaft 20 which is driven from the motor through the intermediation of pinion gear 23, bevel gears 24 and 25,

shaft 26, and connecting gears 27 and 28. Connecting gear 28 is mounted on a common shaft 29 with the sprocket 30 which is driven from the jig rotating motor 21 through the intermediation of sprocket 31 and chain 32.

When a work piece such as the sink 3 is being enameled, certain surfaces will be more steeply inclined with respect to the direction of powder fall than others and will thus require an additional flow of powder if a uniform depth is to be obtained on these surfaces. This may be accomplished conveniently by reducing the speed of the rotation of the drive for the jig 11 when these surfaces are passing beneath the powder fall. In the preferred embodiment of FIGS. 4-6, a non-uniform drive gear 22 is mounted at the bottom of the jig rotating shaft 20 to accomplish this result. The portion A of this gear is formed with an increased diameter to cause the shaft 20 to rotate more slowly when the pinion 23 is engaged with this portion of the gear. In FIGS. 4-6 the enameling position for the sink 3 is shown in dash-dot lines. The gear 22 is so positioned that the jig 11 is carrying the steeply inclined back portions 3 of the sink or work piece 3 beneath the area 36 of powder fall when portion A of the gear is in engagement with pinion 23 and so that the more horizontally positioned bowl portion 3" of the sink is moved beneath the powder fall for the remaining smaller diameter portion of gear 22. In order to compensate for the varying diameter of the drive gear 22, the pinion 23 is slidably mounted on a reciprocable support 37 which is slidably mounted on the bracket member 38 and which is connected to the drive gear 22 by means of the slotted cam 39 in the drive gear 22 and the cam follower pin 40 on the end of the support 37. The bevel gear 25 is slidably mounted on its mounting shaft 26 by a suitable spline to cause the bevel gears 24 and 25 to remain in engagement during the movement of the pinion 23.

Other suitably shaped gears may be used in place of the drive gear 22 to provide for the desired rotational speed changes for any particular work piece so that the work piece is slowed down as its more steeply inclined portions pass under the powder fall.

The same result may be also obtained by varying the speed of the jig-rotating motor 21 manually or by a suitable automatic control such as a cam operated speed control.

Powder Feeders As best illustrated in FIGS. 2 and 3, a main powder feeder 7 is provided to apply the powder to the principal areas of the work piece 3 and an auxiliary powder feeder 8 is also provided which is adapted to apply powder to powder feeders, depending upon the number of differently sloped surfaces on the work piece which must be enameled.

As is best illustrated in FIG. 3, the main powder feeder comprises a U-shaped trough 41 having a powder hopper 42 positioned at one end and a powder feeding edge 43 at its opposite end. When the trough 41 is in use, it is mounted with a slight downward incline towards the powder feeding edge 43 to facilitate the travel of the powder from the hopper 42. In addition, a mechanical vibrator 45 is mechanically attachedto-the trough so that the movement of the powder is further facilitated by the vibration of the trough. The powder hopper 42 also has a suitable mechanical vibrator 46 mounted thereon. In order to provide for movement of the trough 41 into a suitable powder delivery position, a roller-type mounting is provided on the horizontal rails 47 which support the upper frame 48 and the rail engaging rollers 49. The trough 41 is attached to the upper frame 48 by the hangers 50 which have suitable length adjustors 51 to permit the trough to be positioned at a suitable incline to provide the rate of powder feed desired for a particular work piece.

The powderfeeder 8 comprises a U-shaped trough 52 adjustably mounted on a frame 53 which supports it by means of the rollers 54 on rails 55. Arhopper 56 supplies powder to the auxiliary feeder 8, and the powder is moved to a powder feeding slot therein by means of a suitable tilt in the trough 52 in cooperation with the vibratory motion provided by a vibrator 57 on trough 52 and a vibrator 58 on hopper 56.

The details of the powder feeding edge 43 of the main powder feeder 7 are illustrated in FIGS. 9-11. Powder 59 moving down the inclined feed trough 41 under the influence of the vibrator 45 will fall in a radially disposed sheet onto the heated surface of the work piece 3, moving therebelow. Inorderto retain a uniform distribution of the falling powder 62 and in order to prevent bunches or lumps of powder from falling onto the Work piece 3, a sieve-like means is mounted below the open edge 43 of the trough 41. In the preferred embodiment illustrated, this sieve-like means comprises the comb 60 having a plurality of parallel wires or metal tines 61 positioned in the path of the falling powder62. These wires or tines 61, are preferably proportioned so that they vibrate sympathetically with the vibratory action of the feeder trough 41. Lumps or bunches'63 of powder '62 falling onto these fivibrating tines 61 are broken up by'their vibratory movement to a suitable degree for the enameling action.

The tines 61 are sloped upwardly towards their free end 64 so that anylumps 63' which are not broken up by the vibratory motionwill be retained on the tines 61 until they can be removed between enameling operations.

FIGS. 7 and 8 illustrate the powder feeding end of the auxiliary feeder 8 and illustrateanother embodiment of a powder applying edge in slot form. The auxiliary powpositioned adjacent to the free end of the tines 69 prevents the passage of any lumps or powder balls 71 over the ends of the vibrating tines 69. These tines 69 also are prefer ably sloped upwardly towards the baffie 70 to cause the I Depth Control of the Applied Powder As described above, the powder flows downwardly through the vibrating feeder combs or 67 in a generally vertical stream radially directed with relation to the rotating work piece. If the trough of the feeder is level, the powder will fall with a uniform density towards the surface of the work piece. As is described above, a con venient method of spreading the powder over'the surface of the work piece is to rotate the work piece in a jig having a rotatable mounting shaft. When the work piece is thus rotated, it is obvious that the portions of the work piece closer to the rotating shaft are moving at a slower speed than are the portions remote from the shaft. It is therefore desirable to compensate for this difference in speed, as the faster moving outer portions of the work piece will receive lesser amounts of powder than will the slower moving central portions of the work piece.

In FIG. 12 a generally rectangular basin 74 is shown positioned in a jig 75. The jig 75 is rotatably mounted on a suitable work piece holder similar to the abovedescribed work piece holder 6 comprising a central rotatable shaft 76 driven by the gears 77 and 78.

One preferred means of compensating for the difference in surface speed at the outer portions of the basin 74 is illustrated in FIG. 12 and it comprises the tilting of the powder applying trough 85 whereby a relatively shallow portion of thepowder stream 86 in the tilted trough drops onto the more central portion 82 of the rotating basin '74 and whereby an increasing amount of powder corresponding to the increasing depth of the powder stream 86 in the tilted trough 85 is dropped towards the outer edge 84 of the rotating basin 74. Thus, the gradually increasing depth of the powder 86 in the tilted trough 85 provides an increasing density of powder fall towards the outer edges of the rotating basin 74 to correct for the increasing rotational speed of these portions which are more remote from the axis of rotation of the jig 75. i

This correction will be somewhat approximate fora workpiece such as the basin 74, as there are a number of changes in the slope of the basin surface being enameled. Thus the changes in rotational speed across the generally horizontal portion 87 will be relatively large as compared to the more vertical side portion 88 which is generally parallel to the axis of the rotating shaft 76.

; keep it more constant for the portions generally parallel to shaft 76. Thus a curved bottom 89 is provided in the trough'90 having a relatively horizontal portion 91 corresponding to the basin surface 92 which is parallel to the axis of shaft 76. Thebottom has more steeply sloped portions 94 and 95 which correspond to the portions 87 and 84 of the basin 74 which'are at an angle 'to the axis of the shaft 76. The most steeply angled portions 96 and 97 'of the bottom 89 correspond to the basin sections 98 and 99 which are normal to shaft, 76 and which therefore have the greatest change in speed.

The auxiliary feeder 100, which is positioned above the outer side walls 101 and 192 of the rotating basin 74, has a shaped bottom 104 with a sloping portion 105 to compensate for the rotational speed increase at the outer edge of the portion 102 of the basin 74 and a generally flat portion 106 for the portion 101 of the basin 74 which is parallel to the axis of rotation of shaft 76 so that all portions of it which are receiving powder at a given time are moving at the same speed. 7

An additionalcorrection may also be provided in the bottom 89 for the relative angle of the basin surface with relation to the falling powder. Thus the portion 87 of the basin 74 which is normal to the powder'fall will receive a heavier coating than section 92 which is at an angle.; The downward step 107 in bottom 89 increases the powder fall by the necessary increment entirely across the section 92 to compensate for its reduced angle to the powder fall.

FIGS. 12 and 13 are sectional views of the basin 74 illustrating a. diagonal section taken approximately through opposite corners. As basin 74 rotated by the jig 75, the angular positions of the portions of the basin surface directly beneath the falling powder 81 will change with respect to the direction of powder fall. Thus, in the basin 74 illustrated, the angular positions of the basin surfaces beneath the falling powder tend to decrease with respect to the direction of powder fall for the portions of the basin 74 intermediate the basin corners as illustrated by the dash-dot showing 74 of such an intermediate section in FIG. 12 where portions 84' and 87 are at an angle from corresponding portions 84 and 87 in the diagonal section. When the angle of the surfaces with respect to the falling powder does decrease such as for portions 84 and 87', an additional amount of powder must be applied to compensate for the change; One way of accomplishing this result is illustrated in FIGS. 12 and 13 wherein the rotational speed of the jig 75 is reduced intermediate the corner portions by the use of the generally rectangular gear 77 having its greater diameter portions positioned to contact the pinion gear 78 while the portions of the basin intermediate thecorners pass beneath the path of the falling powder stream. This results in a reduction of the rotational speed of the basin 74 at these points to permit a greater powder fall. The greater powder fall contacts the more steeply sloped portions 84' and 87' and provides for a uniform depth of enamel.

Another means of compensating for variations in the speed and position of the surface of the work piece being coated wherein the falling stream of powder is moved is illustrated in FIGS. 1418.

In FIG. 14 a generally rectangular basin 110 is illustrated in the enameling position mounted on a. suitable jig 111 rotated by the drive shaft 112. The basin 110 has three principal portions which are being enameled,

i.e. the bottom 114, the sides 115, and the rim 116. The. powder is applied from an inclined chute 117, as illustrated in the cross sectional view FIG. 14, and portion 118 of the powder is falling on the bottom 114 of the sink, portion 119 is falling on the side walls 115, and the portion 120 is falling on the rim 116. Since the basin 110 is rectangular, it is obvious that the corner portions 121 of the sink will be moving at a faster rate than will be the intermediate portions of the side wall. Thus, unless a compensating means is provided, the enamel coating adjacent the corners 121 will be thinner than the enamel coating over the remaining areas of the side wall 115. A compensating means is provided in the form of a rotatably mounted vane 122 which is positioned in, the path of the falling powder 119 and which is mounted for both rotational and longitudinal movement on the horizontal shaft 124.' The compensating action of the vane 122 is provided as illustrated in FIGS. 15-18.

. In FIG. 16 the vane 122 is stationary in the titled position shown and the powder 119 is being applied at the desired depth on an area 125 midway between the center of the basic side walls 115 and the basin corner 121. Thereafter, as the basin continues to rotate counterclockwise to the position illustrated in FIG. 17, the side walls 115 are positioned progressively further from the shaft 112 and therefore move with increasing speed through the falling stream of powder 119. In order to compensate for the increased speed of the side walls,vane 122 8 is rotated in a counterclockwise direction (FIG. 17) to cause the falling stream of powder to move in the direction of the side walls 115 and to provide a relatively constant speed between the powder and the basin side walls to thus coat the sidewall 115 to a generally constant depth even though the side wall 115 is moving at an increased speed. The rotation of the vane 122 is continued at a gradually increasing rate until the corner 121 of the basin is reached, as is illustrated in FIG. 17 and there after the counterclockwise rotation is continued at a decreasing rate until the side wall area 126 is reached (FIG. 18) which is positioned one quarter of the distance along the sidewall 115 and which corresponds to area 125. Thereafter, the vane 122 is rotated in the opposite direction since the side wall speed is decreasing and the powder stream is moved in the opposite direction to the rotating basin to prevent an accumulation of excess powder. The vane 122 is rotated clockwise at an increasing rate until the basin reaches the position of FIG. 15 with the powder 119 striking the center of side wall 115. Thereafter, the clockwise movement of the vane 122 is continued at a decreasing rate until the basin again reaches the position of FIG. 16 when the vane is stationary and ready for another cycle.

Since the basin illustrated in FIGS. 14-18 is rectangular, it is also clear that the portion of the side wall being struck by the vertical sheet of powder 119 changes its outward position with respect to the shaft 112. Vane 122 is also moved axially in a corresponding degree so that the above-described correction in the powder fall follows the side walls 115 during this irregular motion. This correction is provided by the horizontal movement of the shaft 124 under control of the crank member 128 and a suitably calibrated cam 129 coupled to the jig drive shaft 112. The same cam 129 may also be used to control the above-described rotation of the vane 122, since the change in position of the side walls is proportional to the change inside wall speed. A suitable cam follower 130 connected by bevel gears 131 and 132 moves the vane 122 throughthe above-described powder position ad ustments. As is illustrated in FIG. 14, the various compensating means may be combined. In the trough 117 a sloped bottom 134 is provided to provide a correction to compensate generally for the increase in speed for the outer portions of the rotating basin 110 as compared to the central portions, and the vane 122 is provided to specifically compensate for the variations in speed and position of the basin side walls 115 in the above-described manner. 1

Operation The operation of the automatic dry process enameling py the above-described methodand apparatus is as folows.

The dry enameling operation is commenced by the placement of the work piece 3 having a suitable base coating into the furnace 2 by means of the fork lift 9. The preferred base coating is a relatively thin vitreous enamel coating applied by a wet enameling process such as spraying or dipping. Access to the furnace 2 is gained through the vertically movable furnace door 4. The work piece 3 such as the wash basin illustrated in FIG. 1 is now heated until its temperature is raised above the fusmg point of the powdered vitreous glass which is to be used in enameling its surface. The fusing temperatures of the enameling powders are usually between 1000 F. and l6 00 F., and the furnace and work piece are heated to a higher temperature before enameling such as about 1750" F. When the work piece 3 has reached this temperature, it is removed by the fork lift 9 from the furnace 2 and is placed in the insulated antechamber 5 which is kept at an elevated temperature such as 600 F. to slow down the cooling of the work piece while the powder is automatically applied to the surface of the work piece in the enameling operation. The elevated temperature of the antechamber permits the heated work piece 3 to remain above the fusing temperature of the powder during the entire time which is necessary for the automatic application of the powder to the surface to be enameled by the following operation.

As more completely described above, the work piece is mounted on a movable work piece holder 6 while positioned in the antechamber so that the work piece may be tilted to a predetermined enameling position and may also be rotated about a predetermined axis. The tilt of 10" These movements of the vane 122 are controlled by a rotating cam 129 operatively coupled to the vane 122 and to the drive means for the jig 111 so that the cam 129 and the jig 111 rotate in synchronism. It will be seen that an improved method and means have been disclosed for a dry process enameling of metal the work piece and its rotation about the desired axis are controlled by the tilting motor 16 and the jig rotating motor 21, respectively. The jig 11 is mountedon the work piece holder '6 so that it will support the work piece 3 in a predetermined positionwith respect to the rotational axis of the jig 11. Thus, after the work piece 3 has been properly positioned in the jig 11 by the fork lift 9, the work piece 3 may be moved to its enameling position by the tilting of the jig 11 by' the tilting motor 16. Y

' For each particular shape of work piece, a rotational speed pattern is worked out in accordance with the above discussed principles and the rotation gear, including the drive gear 22, is designed to provide the proper decrease in rotational speed for the more steeply sloped surfaces of the work piece. In the preferred embodiment shown, the work piece 3 is moved in its proper enameling motion by the operation of the jig rotating motor 21 at a predetermined speed. The powder is thereafter applied to the moving work piece 3 from, the main feeder 7 and the auxiliary feeder 8 or other feeders as is necessary. After the troughs 41 and 52 have been moved on rails 47 and 55 into the antechamber 5 to their correct position above the work piece 3, the powder fall is initiated by energizing the hopper vibrators 46 and .58 and the trough vibrators 45 and 57. The powder fall downwardly along the inclined troughs 7 and8 and falls in a predetermined'density through the tines 61 and 69 of the combs 60 and 67, respectively. When the powder strikes the heated surface ofthe work piece 3, it fuses and fiows into a smooth liquid coating of predetermined depth which will harden into the enameled surface when the work piece 3 cools below the fusing temperature.

In order to compensate for changes in rotational speed between the central portions and the outer portions of rotated work pieces, the powder feeding troughs 7 and 8 are tilted so that the powder fall increases towards the outer edgesof the falling stream, as is illustrated in FIG. 12. For work pieces such as that illustrated in FIG. 13 having a relatively non-uniform cross section, a false or curved bottom is placed in the powder feeding troughs. The depth of the powder is adjusted by means of this bottom to progressively increase the powder flow towards the outer edges of surfaces disposed generally at right angles to the axis of rotation of the work piece jig and which therefore have speed changes across their width and to keep the powder flow fairly constant over surfaces disposed parallel to the axis of rotation where there is little change in surface speed over such portions.

An additional compensating means is illustrated in FIGS. 14-18. In this means a vane 122 is positioned in the stream of falling powder and the vane is moved in synchronism with the rotating jig to compensate for changes in the speed of particular portions of the work piece. Thus, as the basin illustrated is rotated beneath the falling powder, its speed past the stream of powder increases for the outer corner portions. The vane 122 is turned to maintain a constant relative speed between the falling ware. The process and means disclosed provide for. a rapid, automatic dry process enameling which is accomplished with a single heating of the Work piece. The method and means disclosed speed up the enameling process by eliminating reheating requirements and pro vide a more rapid and less expensive enameling process by eliminating the series of manual operations heretofore required in the dry process enameling operation.

The method and means disclosed may be used for a variety of metal shapes and may be used on both uniform and non-uniform articles with relatively simple and automatically operated compensating devices which provide for a uniform enamel coating of constant depth.

'As various changes may be made in the form, construction-and arrangement of thepartsherein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be underto a temperature above the melting point of vitreous enamel, thereafter maintaining the temperature of the atmosphere about the work piece substantially above room temperature and below the melting temperature of the enamel, moving the work piece in the atmosphere with laterally spaced surface areas of the work piece moving at different linear speeds, impinging a falling stream of 'dry powdered enameling material through said atmosphere onto said surface areas of said work piece, and supplying said material to said areas of the work piece in quantities predetermined in direct proportion to the rate of speed of the movement of said areas.

2. Apparatus for enameling a metal work piece with vitreous enamel which comprises the combination. of a furnace adapted to heat the work piece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantiallyabove room temperature and below the temperature of said furnace, means for applying enamel indry powdered form tofthe work piece positioned in said adjacent enclosure, means .to movably mount the Work piece in said enclosure beneath said enamel applying means, and a remotely controlled drive means for said movable mounting means.

3. The apparatus as claimed in claim 2 in which said enamel applying means comprises'a powder; retaining hopper, a trough member connected to said hopper at one end and having its other end adapted to enter said adjacent enclosure, an elongated powder dispensing poraxis.

powder and the rotating basin as the speed of the rotating for portions of the basin of smaller diameter which move at lower speeds such as the centers of the side walls.

5. The apparatus as claimed in claim 3 in which said powder dispensing portion comprises an elongated edge of said trough and a sieve-like member beneath said edge portion and extending co-extensively therewith.

7. Apparatus for enameling a metal work piece with vitreous enamel which comprises an enclosure having a heating means adapted to maintain the temperature of the atmosphere in the enclosure substantially above room temperature and below the melting temperature of the enamel, means mounting the work piece in said enclosure for movement with laterally spaced surface areas of the work piece moving at different linear speeds, means for impinging a falling stream of enameling material in dry powdered form onto said surface areas of said work piece including means for supplying said material to said areas of the work piece in quantities predetermined in direct proportion to the rate of speed of the movement of said areas.

8. The apparatus as claimed in claim 7 in which said means for impinging said material comprises a trough member adapted for connection to a source of powdered enamel at one end, said trough movably mounted for the positioning of its opposite end within said enclosure, a vibrating means operatively coupled to said trough to facilitate the movement of powder toward said opposite end, and said trough having its bottom inclined from the horizontal in a direction normal to the direction of the powder movement thereon to permit a greater flow of powder to be applied to the work piece at its relatively faster moving portions and at its relatively more steeply sloped portions.

9. The apparatus as claimed in claim 7 in which said means for impinging said material comprises a trough member, a powderdispensing portion on said trough adapted for positioning within said enclosure, a vibrating means operatively coupled to said trough to facilitate the movement of powder toward said dispensing portion, and

said trough having one or more portions inclined from v the horizontal in a direction normal to the direction of powder movement.

10. The apparatus as claimed in claim 7 in which said means to movably mount the work piece comprises a rotatably mounted jig, and drive means for said jig comprising one or more irregularly shaped gears adapted to rotate it at a non-uniform rate. I

11. Apparatus for applying enamel in dry powdered form to a work piece heated to a temperature at which the powdered enamel will melt to form a smooth enamel surface comprising means producing a sheet-like stream of powdered enamel, a second means movably supporting said work piece for moving said work piece through said stream, and a vane movably mounted for rotary movement and for axial movement laterally of the stream of enamel to vary the position of said stream with respect to said work piece.

12. The apparatus as claimed in claim 11 which includes additional means for coordinating the relative movements of said vane and said work piece in a pre-selected manner dependent upon the shape of said 'work piece.

13. Apparatus for enameling a metal workpiece with vitreous enamel which comprises the combination of a furnace adapted to heat the workpiece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantially above room temperature and below the temperature of said furnace, means for aplying enamel in dry powdered form to the workpiece positioned in said adjacent enclosure, means to movably mount the workpiece in said enclosure beneath said enamel applying means, and a drive means operatively coupled to said movable mounting means and including a speed changing means.

14. Apparatus for enameling a metal workpiece with vitreous enamel which comprises the combination of a furnace adapted ,to heat the workpiece above the melting point of the enamel, an adjacent enclosure having an auxiliary heating means adapted to raise the temperature of the adjacent enclosure substantially above room temperature and below the temperature of said furnace, means for applying enamel in dry powdered form to the workpiece positioned in said adjacent enclosure, means to movably mount the workpiece for motion about two axes in said enclosure beneath said enamel applying means, a pair of drive means each operatively coupled to said movable mounting means for providing the motion.

References Cited in the file of this patent UNITED STATES PATENTS 605,903 I Otto June 21, 1898 707,490 Zwermann Aug. 14, 1902 710,443 Dupont Oct. 7, 1902 759,351 Dawes May 10, 1904 862,285 Schmidt Aug. 6, 1907 1,361,869 Kebler Dec. 14, 1920 1,669,587 Brotz Sept. 23, 1927 2,223,476 Amstuz Dec. 3, 1940 2,360,413 Getz et al Oct. 17, 1944 2,402,183 Rowe et a1. June 18, 1946 2,513,434 Tinsley July 4, 1950 2,572,702 Davis Oct. 23, 1951 2,719,093 Voris Sept. 27, 1955 I 2,789,926 Tinholt et al Apr. 23, 1957 2,792,030 Wahl May 14, 1957 Tafel Sept. 13, 1960 

1. THE METHOD OF ENAMELING A METAL WORK PIECE WITH VITREROUS ENAMEL WITH COMPRISES HEATING THE WORK PIECE TO A TEMPERATURE ABOVE THE MELTING POINT OF VITREOUS ENAMEL, THEREAFTER MAINTAINING THE TEMPERATURE OF THE ATMOSPHERE ABOUT THE WORK PIECE SUBSTANTIALLY ABOVE ROOM TEMPERATURE AND BELOW THE MELTING TEMPERATURE OF THE ENAMEL, MOVING THE WORK PIECE IN THE ATMOSPHERE WITH LATERALLY SPACED SURFACE AREAS OF THE WORK PIECE MOVING AT DIFFERENT LINEAR SPEEDS, IMPINGING A FALLING STREAM OF DRY POWDERED ENAMELING MATERIAL THROUGH SAID ATMOSPHERE ONTO SAID SURFACE AREAS OF SAID WORK PIECE, AND SUPPLYING SAID MATERIAL TO SAID AREA OF THE WORK PIECE IN QUANTITIES 